Dr. Stephen Yen was born in Boston and lived
in different parts of Asia during his childhood. His mother, Chin-Ho Yu Yen,
was a physician and his father, Peter Kai-Jen Yen, an orthodontist who taught
at Harvard for twenty five years. His parents taught Dr. Yen about faith, family
and work as they served two terms as Christian missionaries in Taiwan and Hong
Kong. Dr. Yen's father was a pioneer in the field of orthodontics and founded
departments in Taipei, Hong Kong, Xian, Chengdu, Shanghai, Beijing and Guangzhou.
Dr. Yen graduated from the Harvard School of Dental Medicine before completing
his Orthodontic Residency at the University of Southern California. While completing
his PhD at the Center for Craniofacial Molecular Biology where he currently
conducts research, Dr. Yen worked for two years with Bill Shaw at Children's
Hospital Los Angeles, and later took over the care of the craniofacial patients
at the hospital. At USC, he teaches orthognathic surgery to the oral and maxillofacial
surgery residents and takes part on the joint seminars between the orthodontic
and oral surgery departments. He also works one day per week at the USC-Los
Angeles County Hospital treating adult patients who need reconstructive surgery
due to trauma. He directs a post-residency fellowship in craniofacial orthodontics.
His research interests include surgical-orthodontic treatments for cleft lip
and palate patients and molecular determinants of facial overgrowth. He is married
to Christine Kuida and has three children: Leia, Daniel and Lauren. They add
humor, affection and unpredictability to his daily life.

Luciane Macedo de Menezes

First of all I would like to congratulate
you for the abnegation and brilliance with which you are engaged in the research
of new therapeutic techniques and in assisting patients with severe congenital
deformities. The closing of the alveolar cleft with autogenous donor sites such
as the iliac crest or the chin region, among others, is well established. Taking
that into account, what would be your choice of treatment in the presence of
large oronasal communication in the hard palate region, considering patients
in mixed or permanent dentition? Roberto Rocha

I work with a craniofacial team that has surgeons
from different disciplines - speech pathologists, pediatricians, geneticists,
nurses, child psychologists, pediatric dentists and audiologists - who help
to determine what type of treatment is feasible for each patient. During early
mixed dentition, we may obturate a large anterior palatal fistula to improve
speech. Currently, we are testing the use of Nance appliances in order to provide
patients with an appliance that does not have to be remade every few months.
Our surgeons may opt to first try to close a fistula using soft tissue flaps
from the cheek, tongue or free tissue grafts from other parts of the body with
blood supply. However, one potential problem with soft tissue flaps is post-treatment
expansion that can re-open the fistula during expansion. A narrow arch form
with a large anterior palatal fistula is very challenging to treat. In the past,
we have collapsed cleft segments in order to graft the segments so that they
could be expanded by distraction osteogenesis to provide additional bone and
soft tissue. We have also distracted segments of palatal bone across a palatal
opening by using a tooth or a palatal microimplant (TAD) as a handle for osseous
transport. This requires making custom transpalatal wires for the tooth or TAD
to travel across a palatal opening.

Distraction osteogenesis to lengthen the mandible
in patients with congenital deformities can lead to poor occlusion and open
bite. In order to compensate for problems that occur during lengthening, orthodontic
intermaxillary elastics can be used to guide the distracted mandibular segment.
It is reported that some clinicians remove the distractor before total bone
consolidation to take advantage of the phenomenon called "callus molding". Is
it necessary to remove the distractor before bone consolidation to better mold
the regenerated bone? Eduardo Franzotti Sant'Anna

The "floating bone technique" describes the early
removal of distractors so that the distraction segments can be guided into occlusion
with orthodontic elastics.

Since the center of the distraction site is fibrous,
distraction osteogenesis is an elastic process. If the distractors are removed
too early, then the segments can relapse to its original position. In animal
experiments, we found that early removal of distractors could also cause the
distraction site to buckle in a transverse dimension and cause midline shifts.
If the distractors are to be removed for callus molding, then it should be done
after at least two weeks of bone consolidation, so that there can be some stabilization
of the distraction site. Heavy force elastics are needed to guide the distraction
process. The forces must be continuous to prevent rapid formation of bone across
the distraction site. Intermittent force will lead to early consolidation and
interrupt the distraction process. We tend to get some relapse so I overcorrect
the malocclusion (Fig 1).

Do you have a specific protocol (time to start,
with or without the distractor in place, type of maxillary archwire, elastic
force used and time to stop when the open bite does not close) for callus molding?
Eduardo Franzotti Sant'Anna

If you do not remove the distractor, then orthodontic
guidance can begin as early as the distraction period. If the distractors are
to be removed for callus molding, then the distractors should be left in place
at least for two weeks of bone consolidation. Our animal studies suggest that
callus molding can occur after two weeks, but the rate of correcting an opening
will slow down and may result in only a partial correction while the distraction
site is mineralizing. We are balancing opposite needs: Stabilizing the distraction
site for bone formation vs. maintaining some elastic properties of the distraction
site for open bite correction. Heavy stainless steel rectangular archwires are
used with heavy elastics in order to guide a distraction procedure.

What could be the deleterious effects of redirecting
and manipulating the distraction site (callus molding) with orthodontic elastic
forces? Eduardo Franzotti Sant'Anna

Since heavy elastic forces are needed to guide
distraction procedures, there is always the risk of extruding the tooth out
of bone when heavy elastics are placed against brackets and wire. The extrusion
effect may come later, after an open bite is corrected, but the osseous segment
is relapsing while the bite is held together only by the use of elastics. An
initial skeletal correction can turn into a dental compensation as the segments
pull away from teeth and relapse. This is a paradigm for distraction, protraction
and surgical relapse that we are investigating. In order to produce skeletal
movements and limit skeletal relapse, we add microimplants (TAD) to the orthodontic
guidance protocol so that wire loops will connect the brackets and wire to the
bone. When orthodontic elastics are applied to the archwire, the force will
also be applied against the microimplant in bone.

It is possible to distract a bone graft, but
the quality of the bone graft may not be ideal for distraction. For example,
if there are voids or dips in the level of the bone graft at the distraction
site, then these irregularities will be stretched out during the distraction
process. The ideal bone for distraction is dense, has ideal height and width
and does not contain sutures.

Do you believe that BMP grafts represent a
promising future for the cleft palate patients? Carlos Alberto Estevanell
Tavares

Bone morphogenetic proteins will have a place
in craniofacial surgery in the future but the long-term complications need to
be identified and understood. We are moving away from alveolar bone grafts from
the iliac crests to a combination of BMP2 in demineralized bone matrices. This
bone substitute can eliminate the morbidity of harvesting bone from the iliac
crest. In a study reported at IADR and ACPA this year (2011), we compared autogenous
bone grafts and MP2/demineralized bone matrices. BMP2, as sold in the original
collagen sponge, can be compressed in the cleft site and produce only limited
amounts of volumes of bone. In order to maintain the space and volume, the BMP2
was placed inside a roll of demineralized bone. We studied the graft outcomes
with the Kodak 3000 which has the highest resolution for a cone beam CT and
a limited field of three teeth (Fig 2). We found that neither
type of graft completely filled the cleft site but BMP2 with demineralized bone
matrices produced almost twice as much bone. Interestingly, both types of bone
grafts can show 100% bone fill in the vertical and mesial-distal dimensions
as seen in an occlusal radiograph but only 20-60% bone fill in the missing transverse
dimension. We need to do better in the future.

In your opinion, what are the main indications
for skeletal anchorage in cleft palate patients? Luciane Macedo de Menezes

I use microimplants differently than most orthodontists
because I am not trying to eliminate the surgery. Most craniofacial patients
will need surgery to improve their function and appearance. The microimplants
are used to support surgeries and limit surgical complications. Skeletal anchorage
can help to protract a maxilla, widen a fused maxilla, set up a wire system
for osseous transport and provide anchorage in edentulous spaces.

Do you think skeletal anchorage can reduce
the use of corticotomies? Carlos Alberto Estevanell Tavares

I think corticotomies and skeletal anchorage
can be used together. In terms of anchorage for tooth movement, corticotomies
are a method for reducing resistance to tooth movement whereas microimplants
(TAD) can increase resistance. Both methods can target specific teeth. The combination
of techniques provides a way to alter the bone biology of tooth movement. This
is an area of active research for us, as well as several other laboratories.

Basically, in which situations would you recommend:

- Orthodontic tooth movement associated to
corticotomy?

- Surgically assisted block displacement?

Roberto Rocha

I am a little afraid of losing bone during a
corticotomy procedure which is why, I believe, periodontists place a bone graft
over the dental roots to hold the space for bone remineralization. Most of the
time, I use osteotomy-assisted tooth movement for reshaping the arch form in
craniofacial patients (Figs 3 and 4).
I ligate the segments against the host bone for three days to ensure a good
distraction callus before distracting the segments into position. Corticotomy-assisted
tooth movement is used by some orthdontists to accelerate tooth movement. In
the future, there may be less invasive ways to produce the bone response needed
to accelerate tooth movement.

What are the main challenges in treating children
with congenital malformations?

Luciane Macedo de Menezes

I think the main challenges for the future are
financial and educational.

One challenge is to make the medical and orthodontic
care affordable to patients with congenital malformations through private and
government medical insurance programs.

Another challenge is to help orthodontists to
take care of patients with specialized needs through a post-residency fellowship
such as the one we have in craniofacial orthodontics at Children's Hospital
Los Angeles.

Since the 50's the treatment protocol of cleft
lip and palate patients has evolved and several paradigms have changed. From
your point of view what new boundaries are to be unfolded in orthodontics and
surgery?

Roberto Rocha

Certain innovations such as distraction osteogenesis
and bone morphogenetic proteins have provided new strategies for dealing with
osseous deformities. However, as an orthodontist, one paradigm that has changed
for me is my approach to the Class III malocclusion. I used to be afraid that
any procedure that might worsen a Class III malocclusion would automatically
lead to orthognathic surgery later in the life of the patient. Currently, I
don't worry about Class III malocclusions as much because we now use several
maxillary protraction protocols during adolescence to achieve Class III correction
even in large skeletal Class III cases. These protraction techniques are supported
by alternating expansion and constriction to loosen the sutures, SARPE/LeFort
I surgeries in cases of fused sutures and microimplants to limit side effects
of treatment. The benefits for early interventions used to be weighed against
the post-treatment effects on maxillary growth. The timing of an alveolar bone
graft is such an example. In the past five years, the calculation of risks and
benefits for different procedures has changed for me because I have a way to
deal with Class III malocclusions without orthognathic surgery. The goal in
my research is to re-create the bone response for distraction osteogenesis and
rapid tooth movement in order to eliminate or limit the need for surgery. I
welcome collaborations with colleagues in Brazil to help studying these new
areas of research.

During the period that I had the opportunity
to accompany you at Children's Hospital, the affection and dedication provided
not only to the cleft children but also to their parents called my attention.
I would like to know what was the most important lesson taken from your contact
with these children and their parents?

Luciane Macedo de Menezes

As a clinician, I tend to focus on the anatomical
and functional problems but I have learned from my patients that the most important
part of a person is who they are inside. Perhaps, the hardest task is to help
children develop cheerful and positive personalities despite the physical challenges
they may have. I feel that as orthodontists we can serve as mirrors to help
children see themselves as very special people, made in the image of God.

Carlos Alberto Estevanell Tavares- Dentistry Graduate, Federal University of Rio Grande do Sul State.
- MSc and PhD in Dentistry (Orthodontics), Rio de Janeiro Federal University.
- Professor of the Specialization Course in Orthodontics at the Brazilian Association
of Dentistry of Rio Grande do Sul State.
- Diplomate of the Brazilian Board of Orthodontics and Facial Orthopedics (BBO).

Luciane Macedo de Menezes- Dentistry Graduate, Federal University of Rio Grande do Sul State.
- MSc and PhD in Dentistry (Orthodontics), Rio de Janeiro Federal University.
- Professor of Orthodontics, School of Dentistry, Pontifical Catholic University
of Rio Grande do Sul State.
- Coordinator of the Specialization Course in Orthodontics at the Brazilian
Association of Dentistry, Rio Grande do Sul State.